Bacterial Reaction Centers With New Photochemical Properties

Project: Research project

Project Details

Description

Overview:
Deciphering the mechanisms by which the movements of protons are linked to electron transfer events is an important challenge in understanding biological catalysis. Prof. James Allen and Dr. JoAnn Williams are directing their efforts to elucidating the proton coupling associated with electron donors in light-induced reactions that occur in photosynthesis. The bacterial reaction center, an integral membrane protein serving as the site of the primary photochemistry, will be modified such that the yield of proton and electron transfer can be measured for different cofactors and protein environments. The first objective of this proposal entails a systematic analysis of the contributions of particular amino acid residues to test the idea that proton release from key residues in specific configurations is correlated with electron transfer. In the second objective, they will investigate the complementary hypothesis that the coupled release of protons is directly related to electrostatic interactions determined by the distribution of charge on the donor by measuring the relationship between proton release and the electronic structures of different donors. Experiments in the third objective will establish the requirements for proton release during successive electron transfer steps resulting in high oxidation states of the donor. The experimental methods combine structure-based protein design, enabled by molecular biology and biochemical techniques, with analysis of the properties of the resulting complexes by optical and magnetic resonance spectroscopy. Together, the outcomes will expand the tools available for designing proton-coupled electron transfer reactions for catalysis in biological systems.
Intellectual merit:
Control of the coupling between proton and electron transfer is critical for achieving efficient energy conversion and chemical transformations. However, generation of predictive mechanisms for proton transfer in complex systems requires a more complete understanding of the physical principles. To approach this challenge, the proposed project will help establish molecular concepts that explain how proteins effectively perform proton-coupled multi-electron transfer reactions. In this investigation the bacterial reaction center will form the basis of a unique model system with highly oxidizing electron donors. Novel protein design strategies, such as large-scale changes to add redox-active cofactor-binding domains, will produce the capability of comparing different types of electron donors, including multinuclear Mn-oxide compounds. An exceptional feature of the project is the measurement of both proton and electron transfer synchronized using light. The investigators draw on a deep reservoir of information and skills in elucidating the factors that give proteins in photosynthetic organisms the ability to convert light into chemical energy. This project establishes a framework applicable for understanding the progression of oxidation states in the fundamental water oxidation reactions of photosystem II.
Broader impacts:
The project activities offer societal benefits through broadening participation in science and engagement of the wider community. To overcome traditional low graduation rates and limited participation in science degree programs, this project provides students from a local community college with a personal research experience in a supportive environment that encourages their continuation in science. Based on the success of this effort, the School of Molecular Sciences will offer additional stipends for community college students to perform research at Arizona State University. In another avenue of engagement, students will work with artists to express the scientific concepts behind research in bioenergy and photosynthesis and present their integration of science and art to the local community.
StatusActive
Effective start/end date5/3/197/31/22

Funding

  • National Science Foundation (NSF): $642,000.00

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